Variable Speed Drives:
Reducing energy costs in
meat processing plants
Meat processing operations can cut energy consumption
and reduce energy costs by installing Variable Speed
Drives (VSDs) on electricity-driven equipment -
reducing a pump’s speed by 20% can reduce energy
consumption by more than 50%.
The beef supply chain has become increasingly vertically integrated, a development mainly
fueled by the feedlot industry where most of the larger feedlots own their own abattoirs, or at
least have some commercial interest in certain abattoirs.
In addition, some feedlots have integrated further down the value chain and sell directly to
consumers through their own retail outlets. Some abattoirs have also started to integrate
vertically towards the wholesale level.
Currently, many wholesalers source live slaughter animals (excluding weaners) directly from
farmers or feedlots on a bid and offer basis. They take ownership and slaughter the animals at
an abattoir of their choice, whereafter the carcasses are distributed to retailers.
In some instances, the public can also buy carcasses directly from wholesalers.
The abattoir industry has expanded tremendously in number and capacity. South Africa has
approximately 495 abattoirs, divided into those that are:
• Linked to the feedlot and wholesale sector or owned by municipalities; and
• Mainly owned by farmers and SMMEs.
Meat processing plants, like all other commercial operations, are under increasing pressure
from rising input costs. With energy being a major
contributor to operating costs, optimising plants has
become a priority across the sector: A 20% cut in
energy costs can represent the same approximate
bottom line benefit as a 5% increase in sales.
Variable Speed Drives:
reducing energy costs in
meat processing plants
Key facts and figures for South Africa (2011):
• The beef industry as a whole employs 500 000 people; 2 125 000 are dependent on the
livestock industry for their livelihood.
• Cattle production has increased by 37 000 heads from 13.5 million in 2004 to 13.87 million
• Approximately 60% of cattle are owned by commercial farmers and 40% by emerging and
• 80% of cattle are beef and the remaining 20% dairy.
• Beef is produced throughout South Africa.
Production kilograms depend on quality of grazing, supplementary feeding and infrastructure,
such as abattoirs and feedlots, and not necessarily on the number of cattle available in specific
areas. South Africa’s highly developed transport infrastructure allows for the movement of
cattle and calves from one area to another and even from neighbouring countries.
Beef production is shared as follows:
- Mpumalanga (23%)
- Free State (19%)
- Gauteng (14%)
- KwaZulu Natal (12%)
- North West (11%)
• South Africa is a beef importer ; beef consumption is higher than production -
Competitiveness in the sector
Meat processing plants must control operating costs, electricity being one of the major expenses,
to remain competitive.
Energy is used in all aspects of meat processing. Aside from lighting, steam and water heating
systems, motor-driven equipment contribute significantly to energy consumption and, depending
on the type and size of a facility, can include:
• Dehairing equipment
• Processing equipment
• Refrigeration equipment
• Air compressors
• Boiler pumps
Year Head of cattle slaughtered Production kilograms Consumption kilograms
2010/11 2 880 000 819 600 000 864 000 000
• Bleed table pumps
• Water pumps
• Chilled water pumps
• Wastewater pumps
• Meat grinders
• HVAC - ventilation fans
• HVAC - air handlers
• Waste compactors
Installing Variable Speed Drives (VSDs) on motor-driven equipment is one of the most effective
energy efficiency interventions to reduce electricity consumption and cut energy costs in meat
• Beyond lower electricity bills and reduced operating costs, companies that invest in energy
efficient equipment such as VSDs enjoy additional benefits such as greater reliability,
improved productivity and lower maintenance costs.
What is a VSD?
A VSD, also known as a Variable Frequency Drive (VFD) or adjustable speed drive, is a device
that can adjust the frequency to regulate and adapt motor speed to match the actual demand
required by the system or application it is driving, resulting in a reduction in energy consumption.
VSDs offer a high degree of motor control, accurately varying motor speed according to
demand while also adjusting torque – all within the specifications of a particular manufacturer.
A basic VSD can be used for simple applications - such as to control the speed of a pump or a
fan according to the required load. It can also be interfaced with a transducer, such as a pressure
or flow-rate sensor, and programmed to maintain a particular setting.
More advanced VSDs can be used for precise speed and torque control in complex applications
and can be interfaced with a computing system to provide real-time operating data on the
status and performance of a motor.
Slowing down a pump from 100 to 80% can reduce
motor energy use by up to 50%.
How does a VSD work?
All VSDs work on the same principle: they convert incoming electricity, which is at a fixed
frequency and voltage, into variable frequency and voltage.
When a VSD starts a motor, it initially applies low frequency and voltage, typically 2Hz or less,
which avoids the high starting current that occurs when a motor is started using a direct-on-line
or star-delta starter method. The applied frequency and voltage are increased at a controlled
rate to increase the speed of the motor (load) without excessive current being drawn.
Drives adjust the speed of electric motors to match
the actual demand of the application, thereby reducing
motor energy consumption by 20 to 50%.
How does a VSD save?
VSDs save energy because they prevent motors from using more electricity than required -
many motors are oversized to cope with a maximum demand that rarely or never occurs.
When other control methods are used, such as valves, motors run at full speed and the flow
of the output is mechanically restricted. This is wasteful, because the motor keeps running at its
nominal speed regardless of demand. A pump, for instance, delivers maximum output and the
excess is reduced at the valve where the surplus energy is wasted through friction.
A pump or fan running at half speed, consumes only one eighth of the power compared to one
running at full speed, which means a small decrease in speed requires a lot less power.
VSDs deliver accurate control and less mechanical wear,
reducing maintenance and extending the life expectancy
Putting VSDs to work
Applying VSDs in meat processing plants
Reducing refrigeration costs
Refrigeration is used to preserve meat products. Refrigeration, therefore, accounts for a large
portion of meat processing costs. As such, improving the energy efficiency of refrigeration
systems represents huge opportunities for saving energy.
• Screw and reciprocating compressors and evaporative condensers are widely used
throughout industrial refrigeration applications, from cold rooms through to blast freezing.
When refrigeration demand is low, compressors are switched off in sequence and restarted
when demand increases. Condenser fans use on/off control and vaporator fans are stop-started
as required. This on/off operation is extremely energy inefficient as large amounts of power are
required to get a fan up to full speed; every time an electric motor is started conventionally it
can consume up to 6 times its normal full load. VSDs have a soft starting function to prevent
this from occurring.
VSDs are an excellent tool for optimising the energy consumption of conditioned atmosphere
and refrigeration processes. Since cold storages and refrigeration plants typically run 24 hours
a day, most refrigeration drive applications are candidates for VSDs - any refrigeration system
with a wide variation in operating hours or with variable heat loads that are less than the peak
load, can benefit from a VSD.
• VSDs can also be installed on screw compressors, chilled water pumps and condenser fans.
Appropriately applied in refrigeration systems, VSDs can achieve huge energy savings and
help meat processing plants to cut operating costs and remain competitive.
Taking the load off ventilation systems
Ventilation and air conditioning are some of the biggest consumers of electricity in meat
processing plants. Even in the case of the most energy efficient systems, VSDs can help to
further reduce energy usage by closely matching the speed of the motors that drive these
systems with actual demand.
• When ventilation and air conditioning systems need to provide less cooling than the
maximum load for which they are sized, VSDs allow the equipment to operate at a lower
speed, thereby using less power.
There is a broad range of Variable Speed Drives specifically engineered for ventilation and
air conditioning applications. These can be integrated into a variety of building management
systems (BMS) to improve the flexibility and optimise the efficiency of systems.
• In ventilation and air conditioning systems for large buildings, VSDs on fans save ene